The present invention relates generally to a method and apparatus for treating wood surfaces utilizing tandemly arranged endless abrasive belt and flexible rotary abrader and more specifically to a method, apparatus and system utilizing a cross-belt sander arranged in tandem with first and second angularly disposed elongated flexible rotary abraders, with the abrasive cross-belt portion preferably having an oscillating platen. The apparatus forming the system is arranged so that the angularly disposed flexible rotary abraders contact the work surface as a final operation, and following exposure to the abrasive cross-belt. These multiple operations are accomplished in a single pass of the work through the system. As indicated, improved results are achieved when the cross-belt portion has means for orbitally driving its platen at the work-contacting zone or portion of the belt. The improved wood finishing system of the present invention employs either a single or a pair of sequentially arranged abrasive cross-belt sanders, each being provided with an oscillating platen, together with tandemly arranged and angularly disposed first and second flexible rotary abraders, with the axes of the rotary abraders each being arranged at an acute angle relative to the axis of the work conveyor.
The present invention constitutes an improvement over those certain arrangements disclosed and claimed in my co-pending applications Ser. No. 643,701, filed Aug. 24, 1984, and now abandoned in favor of Continuation application Ser. No. 06/874,342, filed June 13, 1986 and now U.S. Pat. No. 4,651,474, issued Mar. 24, 1987 entitled "Wide Belt Sandin Machine with Platen Oscillating Means", and Ser. No. 735,142, filed May 17, 1985, entitled "CROSS-BELT SANDING MACHINE WITH OSCILLATING PLATEN MEANS", both of which are assigned to the same assignee as the present invention, the substance of which are incorporated herein by reference.
Wood finishing systems employing tandemly arranged abrasive belts and flexible rotary abraders have been known in the past. In the present system, however, the flexible rotary abraders are arranged at an acute angle, preferably between about 40 and 45 degrees, to the axis of the conveyor system carrying the work through the system, and generally at approximately right angles of each other. Also, in the system of the present invention, it has been found that improved properties may be obtained in the finished product when the abrasive belts are provided in the form of cross-belts with orbitally driven platens.
Belt sanders utilizing stationary platens are also known in the prior art, with one such system being disclosed in U.S. Pat. No. 3,832,807, Kiser et al., assigned to the same assignee as the present invention. Cross-belt sanders are also well known, including their basic structural framework along with their basic drum or roller mounting means.
In a typical wood finishing system of the present invention utilizing angularly disposed flexible rotary abraders, a cross-belt or wide-belt sander arrangement may be employed together with a pair of flexible rotary abraders arranged in tandem therewith. The flexible rotary abraders are disposed with their axes generally at an acute angle to the axis of the conveyor belt and at approximately right angles to each other.
In a typical cross-belt sanding machine, a platen base is normally provided forming a sanding head and with an endless abrasive belt being trained over a plurality of rollers or drums, at least one of which is power driven, the balance of the rollers being idlers and/or guides for the belt as it moves through its orbit. In the wood finishing system of the present invention, the platen is preferably interposed between a pair of belt guiding rollers, and furthermore the platen is driven along an orbital path. The combination of the orbital platen cross-belt along with the angularly and tandemly arranged first and second flexible rotary abraders provides a highly desirable surface with enhanced smoothness on the work being treated, with the surface being substantially free of grooves or other defects so as to render the material suitably adapted for such fine applications as furniture, cabinetry, and the like.
In the present method and system, the cross-belt portion utilizes a belt or belts which are driven along a generally rectangular orbit or path, with the drive roller or drum preferably being disposed at one upper corner zone of the belt orbit. A sufficient amount of wrap is provided on the drive roller for it to accomplish its drive function, and with added rollers or drums being disposed closely adjacent to and on either side of the platen normally being idlers and adapted to move in an orbital path with the platen per se. The angularly disposed flexible rotary abraders are normally provided with and driven from a separate or independent power source, such as an electrical motor, with the system employing either a direct or a variable speed drive.
In the system the present invention, it has been found that the utilization of the orbital platen together with the tandemly arranged flexible rotary abraders provide for improved performance in a number of ways. For example, the utilization of this arrangement provides for improved and enhanced surface qualities or properties in the work surfaces. Also, with the combination of orbital platens and rotary abraders, it has been found that it is possible to use a coarser grit on the abrasive cross-belts, with greater belt speeds being possible and useful without sacrificing or reducing the surface properties of the finished product. Accordingly, production rates are improved without deterioration of quality of the work product. As indicated above, either a single cross-belt, or two tandemly arranged cross-belt systems may be utilized for the operation, along with a pair of angularly disposed flexible rotary abraders.
A number of different types of flexible rotary abraders are known. Abrasive media brushes and flap abrasive brushes are known and have been used in the past. Abrasive media brushes utilizing nylon bristles impregnated with certain abrasive media are commercially available with a relatively wide variety of bristle diameters. Bristle diameters ranging in size up to over 150 mils are available. While the individual bristles of the abrasive media brushes, including wire bristles, are rigid due to the inherent physical property of the material of construction, flap abrasive brushes derive their rigidity by virtue of centrifugal forces induced by their rotary motion.
Typically, in the present device, work is fed into the machine by a feed system or conveyor assembly that comprises an endless horizontally oriented conveyor belt, the upper span or flight of which may cooperate with one or more pinch-rolls so as to grip the work and feed it through the machine at a uniform rate, and in a predetermined angular direction relative to the belt. The linear motion or travel of the belt determines the transport axis for the work. Alternatively, and in lieu of pinch-rolls, stationary edge guides or fences may be employed. During a typical sanding operation, of course, the top surface of the work is arranged in contact with the working surface of the abrasive cross-belt. In order to accommodate and adapt the apparatus of the present invention to workpieces having different thicknesses, the conveyor assembly is arranged to be adjustable either upwardly or downwardly toward or away from the plane of the cross-belt platen, the assembly normally being supported against the force or thrust of forces created on the work as it is arranged on the conveyor belt. When two cross-belt head assemblies are arranged in tandem, it is normally desirable to provide for horizontal adjustment of at least one of the cross-belt platen surfaces, relative to the other, in order to compensate for stock removal accomplished through exposure to the first cross-belt assembly. Downstream from the cross-belt assemblies, the flexible rotary abraders are situated in superimposed relationship with the belt, with these abraders being mounted with their axes at an acute angle to the transport axis of the conveyor, and with the surface of the rotary abraders coming into light working contact, under modest force, with the surface of the work passing therebelow. In order to accommodate workpieces of various cross-sectional dimension, the flexible rotary abraders are arranged for adjustment relative to the surface of the conveyor belt, and also to adjust the force exerted by the rotary abraders against the work. Belt sanding apparatus with vertically adjustable conveyors are disclosed in U.S. Pat. No. 3,832,807 referred to hereinabove, and reference is made to the disclosure in that patent for the details of the adjustable conveyor design.